Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing our new design.

The broken lines shown in the FIGURE represent portions of the displayscreen or portion thereof with a graphical user interface that form nopart of the claimed design.

CLAIM We claim the ornamental design for a display screen or portionthereof with a graphical user interface, as shown and described.